Leakage Pattern of Nano-Filled Restorative Resin Materials: A Scanning Electron Microscope Study

MastersStatement of Problem: With the development of nanotechnology, there is growing interest towards studying the behavior property of adaptation of the recent restorative dental biomaterials composed of nanometric particles. Purpose: The study was designed to investigate with scanning electron microscope (SEM), the leakage pattern of microhybrid composite resin and nanofilled composite resin restorative materials and their recommended nanofilled bonding agents. Materials and Methods: Saucer-shaped Class V cavities were prepared on the buccal and lingual surfaces of 35 freshly extracted human 3rd molars. Teeth were then randomly divided into seven groups (G1-G7) according to the restorative material used. G1 to G4 were restored with Z250 composite resin and one of the following bonding agents: (G1): Scotchbond Multipurpose Plus adhesive (control), (G2): Adper Single Bond Plus adhesive, (G3): XP BOND™ Adhesive, (G4): Futura Bond NR. From G5 to G7, the cavities were restored with the previous nanofilled adhesives with their recommended composite resin as follows: (G5): Filtek Z350 with Adper Single Bond Plus Adhesive, (G6): CeramX™ with XP BOND™ Adhesive, and (G7): Grandio with Futura Bond NR. After polishing and thermocycling, teeth were immersed in ammoniacal silver nitrate solution for 24 hours in total darkness, followed by 8 hours of immersion in photo-developing solution with exposure to fluorescent light. Teeth of each group were sectioned mesio-destally, then bucco-lingually (n=20). All cut surfaces were prepared for leakage evaluation and examined under SEM. The length of any gap or silver penetration along the preparation wall was examined under both low X200 and high X1000. Data was analyzed with Kruskal-Wallis test, Tukey HSD test was also used to compare the leakage % between all groups. Results: Restored cavities in all test groups showed nanoleakage pattern except G4 which showed microleakage with gap formation. No significant difference in the leakage % was found between G2, G5, G6 & G7 and the control group G1. However, G3 was the only group that showed significantly higher leakage % than the control group. When comparing cavities filled with each of the nanofilled adhesive resins either with their recommended nanofilled composite resins or with the Z250 microhybrid composite resin, no significant difference in the leakage % was found between G2 and G5. Furthermore, leakage % reduced significantly for G6 compared to G3. G7 showed gap free margins in comparison to G4. Conclusions: All tested materials showed nanoleakage pattern except cavities restored with Z250 composite resin and Furura Bond NR adhesive which showed microleakage with gap formation. None of the bonding systems tested was resistant to dye penetration. However, using each composite material according to manufacturer instructions with its recommended adhesive minimizes leakage at the restoration/tooth interface